Conventionally, a fluid control electromagnetic valve is known. In the valve, a fixed core and a movable valving element are accommodated in a resin body that defines a flow passage through which fluid flows. In this kind of fluid control electromagnetic valve, the movable valving element is reciprocated in the axial direction between an initial position and attraction position as described in, for example, JP-A-2006-153231 corresponding to US2006/0117553A1.
Specifically, the movable valving element is attracted from the initial position into the attraction position as a result of generation of electromagnetic attraction force applied to a movable core of the valving element by the fixed core. Accordingly, the movable valving element is disengaged from a fixed valve seat which is formed from the resin body so as to open a fluid passage. On the other hand, the movable valving element returns to the initial position from the attraction position due to disappearance of the electromagnetic attraction force to be engaged with the fixed valve seat. Consequently, the movable valving element closes the fluid passage. As a result of the opening and closing operations of the fluid passage using such electromagnetic actuation of the movable valving element, a flow of fluid through the fluid passage can be accurately controlled. Particularly, in the structure of JP-A-2006-153231 in which the fluid passage is connected between a fuel tank which stores fuel, and a canister that adsorbs fuel vapor formed as a result of evaporation of fuel inside the tank, control accuracy of a flow of mixture of the fuel vapor and air from the fuel tank toward the canister can be ensured.
It is described in JP-A-2006-153231 that the resin body which accommodates the fixed core and the movable valving element, and the resin body which is formed into the fixed valve seat are formed from the same polybutylene terephthalate and are fixed by caulking to each other. In this case, the polybutylene terephthalate is a resin having a larger linear expansion coefficient than a metal from which the fixed core and the movable core are formed. Therefore, particularly in an environment around an engine as in JP-A-2006-153231, each resin body is subject to heat and easily expanded.
The attraction position among movement positions of the movable valving element is determined depending on a position of the metal fixed core, which attracts the metal movable core, whereas the initial position of the movable valving element is determined according to a position of the fixed valve seat with which the movable valving element is engaged. Accordingly, when the fixed valve seat is disengaged from the fixed core by the thermal expansion of each resin body as described above, the initial position is also separated from the attraction position. As a result, a flow rate of fluid flowing through a clearance between the movable valving element at the attraction position and the fixed valve seat varies in the fluid passage. Thus, accuracy in control of a flow of fluid through the fluid passage may be deteriorated.